Monitoring Irrigation Consumption Using High Resolution NDVI Image Time Series: Calibration and Validation in the Kairouan Plain (Tunisia)

Abstract

Abstract:Water scarcity is one of the main factors limiting agricultural development in semi-arid areas. Remote sensing has long been used as an input for crop water balance monitoring. The increasing availability of high resolution high repetitivity remote sensing (forthcoming Sentinel-2 mission) offers an unprecedented opportunity to improve this monitoring. In this study, regional crop water consumption was estimated with the SAMIR software (SAtellite Monitoring of IRrigation) using the FAO-56 dual crop coefficient water balance model fed with high resolution NDVI image time series providing estimates of both the actual basal crop coefficient and the vegetation fraction cover. Three time series of SPOT5 images have been acquired over an irrigated area in central Tunisia along with a SPOT4 time series acquired in the frame of the SPOT4-Take5 experiment, which occurred during the first half of 2013. Using invariant objects located in the scene, normalization of the SPOT5 time series was realized based on the SPOT4-Take5 time series. Hence, a NDVI time profile was generated for each pixel. The operationality and accuracy of the SAMIR tool was assessed at both plot scale (calibration based on evapotranspiration ground measurements) and perimeter scale (irrigation volumes) when several land use types, OPEN ACCESSRemote Sens. 2015, 7 13006 irrigation and agricultural practices are intertwined in a given landscape. Results at plot scale gave after calibration an average Nash efficiency of 0.57 between observed and modeled evapotranspiration for two plots (barley and wheat). When aggregated for the whole season, modeled irrigation volumes at perimeter scale for all campaigns were close to observed ones (resp. 135 and 121 mm, overestimation of 11.5%). However, spatialized evapotranspiration and irrigation volumes need to be improved at finer timescales.

Extracting Soil Water Holding Capacity Parameters of a Distributed Agro-Hydrological Model from High Resolution Optical Satellite Observations Series

“…From a modeling point of view, the 2D approach of the TNT2 model is considered more appropriate in this non-irrigated and hilly context than 1D model approaches that only simulate evapotranspiration considering NDVI retrieved from satellite remote sensing [57].…”

“…It is important to validate this distribution derived from DEM as it highly impacts the modeling results in term of ETR and Nitrogen uptake by crops (Figure 7). Previous studies have used 1D models based on FAO-56 dual crop coefficient water balance model fed with high resolution NDVI image time series to estimate the spatial evapotranspiration fluxes in semi-arid and irrigated agrosystems [57]. Such models, based on remote sensing are not designed to simulate lateral flows and their impacts on the spatial redistribution of evapotranspiration, which could lead to very different results in the present hilly and non-irrigated context.…”

Assessment of actual evapotranspiration over a semi-arid heterogeneous land surface by means of coupled low resolution remote sensing data with energy balance model: comparison to extra Large Aperture Scintillometer measurements

“…For instance, at plot scale, accurate estimates of seasonal ET and irrigation can be obtained by SWB modeling using high resolution remote sensing forcing as done in the study with the SAtellite Monitoring of IRrigation (SAMIR) model by Saadi et al(2015) over the Kairouan plain. However, for an appropriate 85 estimation of ET, the SWB model requires knowledge of the water inputs (precipitation and irrigation) and an assessment of the extractable water from the soil (mostly derived from, say, actual water content in the root zone, wilting point and field capacity ), whereas, significant bias are found mainly when dealing with large areas and long periods, due to the spatial variability of the water inputs uncertainties as well as the inaccuracy in estimating other flux components such as the deep drainage (Calera et al, 2017).…”

“…Hence, to improve its estimation a reduction factor proposed by Torres and Calera (2010) was applied to deal with this problem in several studies (e.g. Odi-Lara et al, 2016;Saadi et al, 2015). Furthermore, since actual ET is computed based on actual soil 105 moisture status, the limited knowledge of the actual farmers' irrigation scheduling is a further critical limitation for SWB modeling.…”

Evaluation and Aggregation Properties of Thermal Infra-Red-Based Evapotranspiration Algorithms from 100 m to the km Scale over a Semi-Arid Irrigated Agricultural Area

“…Groundwater uptake can therefore be scaled to total cumulative ET on an annual basis at least. Up to now, regional scale evaluation of ET relies on distributed information obtained either through hydrological modeling, Remote Sensing (RS) or a combination of both [2].…”